It has been known for a while that polypropylene carbonate produced in a manufacturing process using carbon dioxide as a raw material is considered important in terms of an eco-friendly resin. Contrary to a process using existing phosgene or dimethyl carbonate, the recent process uses carbon dioxide as a raw material, in turn highly contributing to a reduction in greenhouse gas, which causes global warming. Compared to other polycarbonates, polypropylene carbonate has propylene carbonate as a repeating unit of a molecule and such a repeating unit exhibits competitive tendencies of either generating a cyclic propylene carbonate mono-molecule, which is thermodynamically stable or growing into a polymer. Depending upon a catalyst, the repeating unit may become a cyclic propylene carbonate mono-molecule or, otherwise, grow into a polypropylene carbonate polymer. In the case where the polypropylene carbonate polymer is exposed to heat and receives active energy for thermal degradation, the polymer may begin to be degraded by thermodynamic equilibrium. A mechanism for thermal degradation of polypropylene carbonate may be generally classified into two types: scissoring, wherein any part in the middle of a molecular ring is broken, and back-biting, wherein a cyclic propylene carbonate is separated in a series from the end of molecule. According to studies in the related arts, it was reported that reacting a hydroxyl group at the end of polypropylene carbonate with an organic acid such as acetic acid anhydride or phthalic acid anhydride and sealing the same using an ester group may increase thermal stability. However, the above method must adopt esterification under a catalyst, after preparing the solution by dissolving polypropylene carbonate in a solvent. Therefore, in order to apply the foregoing method to commercial manufacturing, an additional reaction process and a drying process to remove a solvent are necessary, thus causing difficulties in ensuring desired low cost production.